Mr. Pop and Mr. Bowie, seated on the floor — they had decided chairs were not natural — were waiting for the Armed Forces Network telecast of “Starsky & Hutch.” The network started shows with a call signal that, Mr. Pop said, went “beep beep beep, beep beep beep beep, beep beep beep,” the rhythm, which is also like a Motown beat, that was the foundation for “Lust for Life.” Mr. Pop recalled, “He wrote the [chord] progression on ukulele, and he said, ‘Call it “Lust for Life,” write something up.’”